I'm looking carefully at the rules as posted to http://www.hardlink.com/~markdu/OWFi...eExplorer.html . The "Oneworld carrier change" provision comes under heading "After ticketing deadline" -- which as is distinguished from "after departure" in which date/time changes are permitted at no charge, but there's no mention of Oneworld carrier changes (provided origin, destination, connect points, and inventory remain the same).

This makes me concerned that I actually can't change carriers for this segment now, after departure.

Others' experiences? Or closer/better readings of the rules?

I do think this will be OK at the airport, but I'd rather not take my chances.